Goodwill and Other Intangible Assets (Details 1) (USD $) In Thousands, unless otherwise specified	11 Months Ended	12 Months Ended
	Nov. 30, 2010	Nov. 30, 2011
Intangible Assets
Gross cost	$ 4,842	$ 23,161
Accumulated amortization	(1,728)	(3,145)
Net carrying amount	3,114	20,016
Exchange and clearing organization membership interests and registrations [Member]
Intangible Assets
Gross cost		11,219
Accumulated amortization		0
Net carrying amount		11,219
Customer Relationships [Member]
Intangible Assets
Gross cost	4,742	10,542
Accumulated amortization	(1,726)	(2,776)
Net carrying amount	3,016	7,766
Weighted average remaining lives (years)	4.2	6.9
Trade names (intangible assets) [Member]
Intangible Assets
Gross cost		1,300
Accumulated amortization		(361)
Net carrying amount		939
Weighted average remaining lives (years)		1.1
Other Intangible Assets [Member]
Intangible Assets
Gross cost	100	100
Accumulated amortization	(2)	(8)
Net carrying amount	$ 98	$ 92
Weighted average remaining lives (years)	14.8	13.8